You need to install NodeJS on your machine. For the best experience VSCode is also recommended. To install the repositories dependencies run
npm i
The core part of this repository is the PowerUs Flights API which provides an endpoint to receive flight data from several sources. You can run the server with the command
npx nx run flights:serve
which means that we run the serve target of the flights app. The configuration for the app is available in the project.json. The server is then available under http://localhost:3333/api.
To test the API manually, you can either open your browser and type http://localhost:3333/api/flights, which performs an HTTP get request to that URL. Or you install the VSCode extension Thunder Client and import the collection saved under ./tools/powerus-flights-api-collection.json.
Start the app as usual. Navigate to the VSCode debugger, select Attach to NestJS API and run it. The debugger is configured in a way that it auto attaches when the app is served and refreshes on save.
The flights endpoint works in the following way: When a request to the GET /api/flights
endpoint is triggered, the server requests ressources for each of the available endpoints.
The endpoints can be defined in the environment files of the API. For each individual
request it checks if there is an existing and valid (by time to life) in
the cache. If that's true, it returns the cache entry. Otherwise it makes the request
to the endpoint with a retry strategy of 3 times (because the endpoints are not
stable). When the response arrives, it validates the response, and formats it into
a suitable format for a list of flights (for each flight having an ID for example).
Once this is done, the request gets stored in the cache.
When all of the individual requests are ready to be processed, they will be merged with removed duplicates and returned to the client. The following diagram should visualize the whole process. With this strategy in place it is unlikely that an endpoint completely fails and the users will face "longer" requests only once every time a cache expires (every hour). If there is constant traffic, a significant amount of users will hit the cache and get quick responses.
